(1) Field of the Invention
The present invention relates to a method for rinsing plate shaped articles, such as semiconductor wafers, particles and masks used in production of semiconductor devices, and to a cleaning bath and a cleaning equipment used in the method for rinsing the plate-shaped articles.
(2) Description of the Related Art
In, for example, a production process of a semiconductor device, after semiconductor wafers are treated with chemicals, the semiconductor wafers are rinsed using, for example, pure water. In particular, in a rinsing process to be performed immediately before a heat treatment process, or a CVD process, small particles must be completely removed from the surfaces of the semiconductor wafers with the metal impurity.
The semiconductor wafers are conventionally rinsed as follows.
Semiconductor wafers are set one by one in supporting grooves arranged at predetermined intervals in a carrier. The carrier in which the semiconductor wafers are set is immersed in cleaner liquid filling a cleaning bath, so that a plurality of semiconductor wafers are rinsed in one lot in the cleaning bath. In addition, a rinsing method has been also proposed in which edges of a plurality of semiconductor wafers are held by a robot hanger in one lot, the semiconductor wafers held by the robot hanger being then immersed in a cleaner liquid so as to be rinsed.
In the above method in which the semiconductor wafers set in the carrier are rinsed, each of the semiconductor wafers 10 is set in a supporting groove 11a formed in the carrier 11, as shown in FIG. 1(a). When the carrier 11 in which each of the semiconductor wafers 10 are set in the supporting groove 11a in the manner as shown in FIG. 1(a) is transported, for example, from a chemical bath to a cleaning bath, an edge of each of the semiconductor wafers 10 vibrates due to the vibration of the carrier 11 in the transportation as shown in FIG. 1(b). In a case where the edge of each of the semiconductor wafers 10 vibrates in the supporting groove 11a, particles are generated. When the carrier 11 is formed of fluoroplastics softer than material (e.g. silicon) forming the semiconductor wafers, powder of the fluoroplastics is generated as the particles. When material formed of the carrier 11 is harder than silicon forming the semiconductor wafer, powder of the silicon is generated as the particles. These particles collect in the supporting grooves 11a.
When the carrier is brought into still water and the supporting groove 11a reaches the surface S of the still water in the above state where the particles have collected in the supporting groove 11a of the carrier 11, the particles P collected in the supporting groove 11a float and are dispersed on the surface S of the still water, as shown in FIG. 2(a). When the carrier is further put under the still water, the particles P floating on the surface S of the still water are drawn toward the surfaces of each of the semiconductor wafers 10 as shown in FIG. 2(b). Thus, when the carriage 11 is pulled up from the still water, the particles adhere to the surfaces of each of the semiconductor wafers 10. In a case where the semiconductor wafers 10 are treated with hydrofluoric acid, the surfaces of each of the semiconductor wafers 10 have a hydrophobic property. In this case, it is particularly easy for the particles to adhere to the surfaces of each of the semiconductor wafers 10.
In a case where a plurality of semiconductor wafers whose edges are held by the robot hanger 5 is immersed in the cleaning liquid so as to be rinsed as shown in FIG. 3, particles are generated at portions at which hanger arms 5a, 5b and 5c supporting the semiconductor wafers are in contact with the edge of the semiconductor wafers 10 as shown in FIG. 4.
In an actual cleaning equipment, still water is not used for rinsing the semiconductor wafers. That is, the cleaning liquid (e.g. the pure water) 100 is jetted from a pipe provided on a bottom surface of a cleaning bath 20, as shown in FIGS. 5 and 6. In a state where the cleaning liquid 100 overflows from the cleaning bath 20, the semiconductor wafers 10 supported by, for example, the robot hanger 5, are immersed in the cleaning liquid 100. When the cleaning liquid 100 is jetted from the pipe 12 on the bottom surface of the cleaning bath 20 and the cleaning liquid 100 overflows from the cleaning bath 20, streams are formed on the surface of the cleaning liquid 100 as shown in FIG. 7. That is, streams generated in the circumference of the cleaning bath 20 uniformly travel toward the outside thereof, but streams generated in the middle of the surface of the cleaning liquid 20 are randomly directed. When the semiconductor wafers 10 are carried into the cleaning liquid in this state, the particles floating on the surface of the cleaning liquid 100 as described above stay on the surface of the cleaning liquid 100 for a long time. As a result, when the semiconductor wafers 10 are pulled up from the cleaning liquid 100 after immersing the semiconductor wafers 10 in the cleaning liquid 100, a probability that the particles floating on the surface of the cleaning liquid 100 adhere to the surfaces of each of the semiconductor wafers 10 increases. Thus, the particles are not completely removed from the semiconductor wafers 10.